With the advent of biotechnology nowadays, rather than conventional plant breeding approaches, genetically modifying a crop trait to enhance the agricultural productivity as well as to meet the increasing demands for the industry is possible. For example, oil bearing plants could be genetically modified through the expression of incorporated foreign genes in their genome, thereby manipulating the fatty acid composition thereof for nutritional or functional purposes. Studies showed that the β-ketoacyl-ACP (acyl carrier protein) family of synthase enzymes (or also referred to as KAS) play a critical role in the fatty acid elongation system. The KAS enzyme catalyzes formation of carbon-carbon bonds by condensing a variety acyl chain precursors, which are generally the malonyl or methyl malonyl moieties from malonyl-ACP. There are four KAS enzymes: KASI, KASII, KASIII and KAS IV. KASII catalyzes the condensation of C18:0 with substrates C14-C16 acyl-ACP. It is, therefore, suggested that an increased in C18: chain fatty acids in plant oils could be observed by expressing in a transgenic plant the gene encoding the KAS II protein.
Accordingly, increasing attempts in isolating nucleic acid fragments encoding KAS protein, from either plants or microorganisms, have been known for oil crop's genetic engineering. For instance, US2004132189 (A1) describes a method of transforming a plant with a DNA sequence encoding β-ketoacyl-ACP synthase (KAS), which is derived from cynobacterial sources, and improves the oil quality of crops, especially soybean. Transgenic soybean seed based on this genetic modification method have a total saturated fatty acid of less than 3.5% compared to that of the wild type.
Another prior art document, U.S. Pat. No. 5,500,361 also describes the use of a β-ketoacyl-ACP synthase II gene isolated from soybean seed, to control the amount ratio of palmitic acid and stearic acid in oil-producing crops. Besides that, as disclosed in prior art document U.S. Pat. No. 6,348,642 (B1), a nucleic acid fragment encoding β-ketoacyl-ACP synthase derived from Ricinus communis, was incorporated into a host genome in an anti-sense orientation, and has shown to improve the lipid profile of the transgenic plant.
Since the KAS II protein shows a promise in the areas of plant oil modification, therefore, it is the primary object of the present invention to isolate a nucleic acid fragment encoding β-ketoacyl-ACP synthase II (KASII) from Jessenia bataua, which is rich in oleic acid content and has a low concentration of saturated fatty acid.
It is yet another object of the present invention to provide a recombinant DNA construct having a nucleic acid fragment encoding Jessenia β-ketoacyl-ACP synthase II (KASII) to transform oil crops, and thereby manipulating lipid profile thereof.